Monitoring the prevalence of nitrosamines in South African waters and their removal using cyclodextrin polyurethanes

Abstract

The prevalence of nitrosamines, especially N-nitrosodimethylamine (NDMA), was monitored in three South African water supplies. NDMA a disinfection by-product (DBP) and potent carcinogen, has recently been detected in many drinking water supplies internationally. Besides direct industrial or human-derived contamination, nitrosodimethylamine can be formed through a chemical reaction between monochloroamine and an organic based compound such as dimethylamine which is frequently detected in surface water. It has been suggested that chloramination of surface waters with a high concentration of dissolved organic carbon (DOC) could result in elevated NDMA formation. Growing evidence suggests that NDMA occurs more frequently and at higher concentrations in drinking water systems that practise chloramination compared to systems that use chlorination. In gauging the extent of water contamination by nitrosamines in water distribution systems, especially NDMA, water samples collected from three different water treatment plants that practise chemical drinking water disinfection were qualitatively analysed for the presence of nitrosamines. Solid phase microextraction (SPME) was employed in the extraction of nitrosamines from the water samples and gas chromatography–mass spectrometry (GC–MS), was used in the analysis of the water samples. Trace amounts of NDMA were detected at one of the water treatment plants and in the distribution network. The application of water-insoluble cyclodextrin (CD) polymers in the removal of nitrosamines and potential amine precursors from the water samples was tested. Quantitative removal of NDMA (based on peak area) from the water samples was achieved which suggests that in the water treatment train the use of these nanosponges can be applied in the mitigation of trace contaminants such as NDMA.